Quark-gluon interaction

Let us turn to papers on the theory of elementary particles published by Ya.B. in the 1960s and 1970s. The 1960s brought into the physics of elementary particles the quark hypothesis. Theorists were on the verge of creating a quantum chromodynamics, a theory of quark-gluon interaction. 

This technique becomes problematic when the particles touch—for example, for the constituents of atomic nuclei. Already, spin forced us to consider quantization without potentials. Many other strange quantum numbers have been posited, with no help from continuum mathematics. Perturbation expansions become funny, since the interaction is no longer smaller than some overriding field. Nucleon-nucleon potentials are discussed in terms of pion exchange, and may also be discussed in terms of quark-gluon interactions. 

The Lagrangian for the quark-gluon interaction is then proportional to... 

As mentioned above, the perspective of this chapter is that of a nuclear system composed of neutrons and protons. The subnuclear aspects of the field are not addressed, for example, the origin of the nucleon-nucleon force and spin, quark-gluon degrees of freedom, and weak-interaction physics. For an overview of these subjects, see (NRC 1999). 

While, in the BCS theory, such attractive force for electron Cooper pair is provided by phonons, for dense quark matter, where phonons are absent, the gluon exchange interaction provides the attraction, as one-gluon exchange interaction is attractive in the color anti-triplet channel1 One therefore expects that color anti-triplet Cooper pairs will form and quark matter is color superconducting, which is indeed shown more than 20 years ago [13, 14],... 

At intermediate density, quarks and gluons are strongly interacting and gluons are therefore presumably screened. Then, QCD at intermediate density may be modeled by four-Fermi interactions and higher-order terms by massive gluons. 

Recently, the possible formation of diquark condensates in QCD at finite density has been re-investigated in a series of papers following Refs. [1, 2], It has been shown that in chiral quark models with nonperturbatrive 4-point interaction motivated from instantons [3] or nonperturbative gluon propagators [4, 5], the anomalous quark pair amplitudes can be very large - of the order of 100 MeV. The diquark pairs that are formed as a result of the attractive inter-... 

For nucleon-nucleon strong interactions within nuclei, pions (= two-quark particles see below) may be the mediating particles Gluons are probably not involved directly, since the nucleons have no "color charge." The inter-nucleon potential goes to zero beyond 1.7fm = 1.7 x 10-15m. 

This crude model tries to show the confinement of three quarks ["up" (u), "conjugate up" (u), and "down" (d), with electrical charges +2/3, +2/3, and -1/3] inside a proton. The springs depict the mutual interactions, meditated by virtual gluons, which are (somehow) limited by the inter-quark potential to remain within the inside of the proton. 

Applications of DFT are foreseen and start to be used in quantum chromodynamics, the theory of strong interactions that study the most elementary particles, like quarks and gluons. Protons and neutrons are composed of quarks that are held together by gluons. These nucleonic... 

Gluon - A hypothetical particle postulated to take part in the binding of quarks, in analogy to the role of the photon in electromagnetic interactions. 

The well-known proton, neutron, and electron are now thought to be members of a group that includes other fundamental particles that have been discovered or hypothesized by physicists. These very elemental particles, of which all matter is made, are now thought to belong to one of two families namely, quarks or leptons. Each of these two families consists of six particles. Also, there are four different force carriers that lead to interactions between particles. The six members or flavors of the quark family are called up, charm, top, down, strange, and bottom. The force carriers for the quarks are the gluon and the photon. The six members of the lepton family are the e neutrino, the mu neutrino, the tau neutrino, the electron, the muon particle, and the tau particle. The force carriers for these are the w boson and the z boson. Furthermore, it appears that each of these particles has an anti-particle that has an opposite electrical charge from the above particles. 

The six quarks, namely the up quark (u), the down quark (d), the strange quark (s), the charm quark (c), the top quark (t), sometimes also called truth quark, and the bottom quark (b), also dubbed beauty quark, carry a colour charge. The bosons that act on colour, are called gluons, which are the carriers of the colour interaction. The residue of this interaction is the strong nuclear interaction, which is operative between the hadrons (for instance the proton and the neutron within an atomic nucleus). 

For unknown reasons, physics is based on the interaction of objects of spin 4 (like electrons or quarks) mediated by objects of spin 1 (like photons, gluons, or W particles). This principle is described by Richard Feynman (see the Additional Literature section later in this chapter). 

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